Sestertius - Augustus ROM ET AVG, altar of Gauls

The Altar of the Three Gauls at Lugdunum — modern Lyon — was established by Drusus in 12 BC as the administrative and religious focal point of the three Gallic provinces. The altar itself was a real structure, constructed at the confluence of the Rhône and Saône, where delegates from sixty Gallic tribes gathered annually on August 1st to conduct rites in honor of Rome and Augustus. Coinage referencing this cult was struck at Lugdunum rather than Rome, tying the physical mint to the monument it commemorated.

RIC 231A falls in the final years of Augustus's reign, when the Lugdunum mint was handling the bulk of bronze production for the western empire.